An achromatic lens, or achromat, is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses are corrected to bring two wavelengths, typically red and blue, into focus in the same plane. Achromatic lenses are often designed by either cementing two elements together or mounting the elements within a housing. This creates smaller spot sizes than comparable singlet lenses. Achromatic lenses are ideal for a variety of applications, including fluorescence microscopy, image relay, and spectroscopy.